Predictors of Work-Related Musculoskeletal Disorders among Commercial Minibus Drivers in Accra Metropolis , Ghana

Background. The objective of this study is to determine the prevalence and predictors of work-related musculoskeletal disorders (WMSDs) among a sample of commercial minibus drivers in the Accra Metropolis of Ghana. Methods. The participating drivers (n = 148)were recruited fromvarious lorry terminals and assessed by using a semistructured questionnaire that included theNordic Musculoskeletal Questionnaire (NMQ). Results. Of the 148 drivers, 116 (78.4%) reported having WMSDs during the previous 12 months. The prevalence of the various WMSD domains was low back pain (58.8%), neck pain (25%), upper back pain (22.3%), shoulder pain (18.2%), knee pain (14.9%), ankle pain (9.5%), wrist pain (7.4%), elbow pain (4.7%), and hip/thigh pain (2.7%). Multiple logistic regression analysis adjusted for possible confounders showed that less physical activity (OR = 4.9; 95% CI = 1.5– 16.5; P = 0.010), driving more than 12 hours per day (OR = 2.9; 95% CI = 1.1–7.8; P = 0.037), and driving at least 5 days per week (OR = 3.7; 95% CI = 1.4–9.4; P = 0.007) were significantly associated withWMSDs among this cohort of drivers. Conclusion.These modifiable factors may be targets for preventive strategies to reduce the incidence ofWMSDs among occupational minibus drivers in Ghana.


Introduction
Musculoskeletal disorders (MSDs) include a wide range of musculoskeletal diseases and syndromes, which are usually associated with pain and discomfort.Work-related musculoskeletal disorders (WMSDs) are defined as impairments of the musculoskeletal system (including nerves and blood vessels) caused or aggravated primarily by work itself or by the environment in which work is performed [1].They occur predominantly in the back, neck, upper extremities, and in some cases, lower extremities, causing significant pain and discomfort with disability and hospitalization (in severe cases).Data show that worldwide, WMSDs account for 42%-58% of all work-related illnesses [2,3] and 40% of all work-related health costs [2].WMSDs are a serious public health problem given the high cost to the injured worker, his or her family, employers, and society to a large extent.The aetiology of WMSDs is multifactorial.The risk factors include awkward posture, manual handling, heavy lifting, strenuous task, and repetitive actions, while demographics, workload, and psychosocial factors are known to influence the development and progression of these disorders [2].Environmental factors (such as temperature, noise, and light complaints) have also been cited as important risk factors of WMSDs [3].

Advances in Epidemiology
The prevalence and risk factors of WMSDs among drivers would vary between countries due to differences in racial background, geographical location, ethnicity and socio-demographics.Although considerable epidemiological studies have explored and reported on musculoskeletal disorders among occupational drivers, few studies have been conducted in Africa and almost none in Ghana to date.An earlier report by our group [16] found a 70.5% prevalence rate of WMSDs among taxi drivers in Accra Metropolis, hence the need to replicate this study among commercial minibus drivers in the same setting.The present study seeks to determine the 12-month prevalence, body distribution, and predictors of WMSDs among a sample of occupational minibus drivers in Accra Metropolis, Ghana.

2.1.
Participants.This epidemiological cross-sectional survey was conducted among 200 commercial minibus drivers (all males) at various lorry terminals in the Accra Metropolis.Eligibility for participants was as follows: being commercial minibus driver, aging 18 years or older with at least one year experience at the current job, and having no history of traumatic road or work accidents.

Data Collection.
A previously validated semistructured questionnaire was administered at interview to each participant while waiting at the lorry terminals.Participation in the study was voluntary and informed consent was obtained from each participant.The three-part questionnaire, which included the standardized Nordic Musculoskeletal Questionnaire (NMQ), was used to determine participants' sociodemographic variables such as age, marital status, religion, education, alcohol consumption, smoking status, and level of physical exercise.Participants who could neither read nor write English were assessed using a validated and standardized translation of the questionnaire (in the local Ghanaian language).Alcohol consumption was defined as the intake of at least one bottle of an alcoholic beverage per week.Physical activity was defined as any activity causing slight-tomoderate increase in breathing or heart rate for at least 30 minutes.A participant who smoked at least one cigarette a day was classified as a smoker.
The questionnaire also assessed occupational factors such as car ownership and driving time profile (years of driving, total driving hours per day, and number of days per week of driving) and psychosocial factors such as self-perceived job stress and job satisfaction of the participants.[20], which is a useful tool for collection of data on self-reported musculoskeletal discomfort and sickness absence.The NMQ is a validated [20][21][22] tool consisting of a general questionnaire for analysis of the point prevalence (7 days), period prevalence (12 months), and severity or disability (effect on normal activities over the last 12 months) of musculoskeletal trouble in different body areas such as neck, shoulders, elbows, wrists/hands, upper back, lower back, hips/thighs, knees, and ankles/feet.The present study assessed the period prevalence of MSDs.The NMQ was chosen because it is standardized, widely accepted, easy to administer, and cost efficient.(IBM Corporation, USA).First, univariate logistic regression was used to obtain estimates of the prevalence odds ratio (POR) of independent factors associated with MSDs.Significant variables were entered simultaneously into a multiple logistic regression model to obtain estimates of the adjusted POR.In all statistical analyses, a value of  < 0.05 was considered significant.

Response Rate and Sociodemographic Characteristics of the Respondents.
Out of the total 200 drivers that were contacted, 36 declined participation while 16 terminated participation when passengers arrived, leaving 148 complete questionnaires for final analysis.Participants' sociodemographic characteristics are presented in Table 1.The mean age of the participants was 33.0 ± 10.6 years (range: 20-54 years).A majority of the participants were married (75.6%),Christians (79.1%), primary and junior high school leavers (54.7%), and employee-drivers (82.4%).The mean number of years of driving was 5.0 ± 3.2 years while the average duration of driving per day and per week was 12.4 ± 2.2 hours and 4.9 ± 0.7 days, respectively (not shown in the table).Many (74.3%) of the participants perceived their job as stressful while 61 (43.9%) of them were dissatisfied with their current job.More than half (56.1%) of them took alcoholic beverages, 23% smoked cigarettes, while 14.2% were engaged in some form of sports/physical activities.

Discussion
This study supports the finding of our previous study [16] and those of other researchers [4][5][6][7][8][9][10][11][12][13][14][15][16] that WMSDs are highly prevalent among drivers.Whereas the prevalence of WMSDs (78.4%) in this study falls within the 53%-91% prevalence range in the worldwide database for drivers, it is lower than the 91% rate reported among stage rally drivers [15] and 81% among truck drivers [5] in Europe.It is also lower than data from Nigeria [23] (i.e., 89.3%), but higher than 70.5% found among taxi drivers from the same setting with similar sociocultural characteristics [16].A further observation of 58.8%rate of low back pain (the predominant musculoskeletal symptom in this study) is close to the 60% prevalence rate among truck drivers in the United Kingdom [5] and 60.4% among commercial vehicle drivers in Malaysia [14] but lower than 64.8% [23] and 73.5% [24] prevalence rates reported among occupational drivers in Nigeria.It is however higher than 34.3% in the previous study among taxi drivers [16].These variations could, in part, be due to differences in methodology, sample size, population (race and ethnicity), and comorbidities.From this study, prolonged driving duration (i.e., >12 hour/day and ≥5 days/week) was significantly associated with increased odds of WMSDs among the drivers.Prolonged sitting (static posture) or muscular inactivity can exert tension (load) on the musculoskeletal structures, thus leading to musculoskeletal discomfort.A relationship between longer duration of driving and musculoskeletal discomfort is supported by several studies [9][10][11]16].
Religion, self-perceived job stress, and dissatisfaction of job, all of which were independently associated with WMSDs in this study, lost their respective associations after adjusting for driving duration.The observed association between religion and WMSDs in this study could be attributed to selection bias.Psychosocial factors such as self-perceived job stress and dissatisfaction of job can lead to psychosocial stress.The exact mechanism underlying the relationship between workrelated psychosocial stressing factors and WMSDs is unclear; however, it is hypothesized that psychosocial stressors interact via complex neurogenic and neuroendocrine pathways to cause muscle tension, spinal cord strain, and fatigue that could predispose drivers to traumatic injury [12].Burnout and musculoskeletal pain are related, but the strength of the associations varies according to gender and occupation [25].An association between psychosocial stressors (selfperceived job stress, dissatisfaction of job, and poor mental health) and WMSDs is supported by other studies among drivers [10,11,16].
Lack of physical activity was associated with increased odds of WMSDs among the participants in this study even after adjusting for possible confounders, suggesting that physical activity may be important in reducing WMSDs of drivers.Although there is evidence that physical activity enhances health [26,27], literature on the relationship between physical activity and WMSDs in working populations is still inconsistent.While some studies [28,29] have indicated favourable relation between the frequency of leisure time sports activity and WMSDs, others [26,30] found no association between the duo while some [31] reported adverse effects of sports activities on WMSDs.This relationship has to be studied further.
Contrary to previous studies [9,10,12,23], the present study found no statistically significant association between musculoskeletal discomfort and other variables such as age, number of years of driving, alcohol drinking, smoking, or ownership of vehicle.Compared with taxi drivers in the same setting [16], it seems that occupational drivers vary in terms of prevalence and predisposing factors of WMSDs.The relatively higher prevalence of WMSDs among minibus drivers in this study could be attributed to the generally bad conditions of these vehicles in the Accra Metropolis.Given OR: odds ratio; aOR: adjusted odds ratio; CI: confidence interval.
the differences in the vehicle and work tasks between taxi drivers and minibus drivers it is likely that the exposure to risk factors would vary between these drivers.

Conclusion
The 12-month prevalence of WMSDs among commercial minibus drivers in Accra Metropolis is high (i.e., 78.4%).
WMSDs in this population were significantly associated with less physical activity and longer driving duration.These modifiable factors may be targets for preventive strategies to reduce the incidence of MSDs among occupational minibus drivers in Ghana.Further studies are required.

2. 4 .
Statistical Analysis.Data were categorized and analyzed with Statistical Package for Social Sciences (SPSS) for Windows, version 20.
Data are presented as frequencies and percentages.Total percentages may not be exactly 100% due to approximations.

Table 2 :
Factors associated with MSDs among the participants ( = 148).Number of subjects with MSDs/number of subjects in each category.* Muslims and other religions combined due to very low frequency of the latter.